Single Metrology Target for Multiple-Patterning Overlay Measurement
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Solution Overview
Problem
Current metrology techniques require separate measurements for each patterning step in multiple-patterning processes, leading to increased substrate area occupation and measurement time for overlay metrology, which is inefficient and time-consuming.
Innovation Solution
A method that uses a single metrology target combining features from multiple patterning steps to directly measure the average overlay performance parameter, allowing for a single asymmetry measurement that can be used to calculate the combined overlay between layers, thereby reducing the need for additional target area and measurement time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate metrology targets are used for each patterning step in multiple-patterning processes, then overlay measurement can be performed for each layer, but the substrate area occupied by metrology targets increases and measurement time doubles
Solution Approach 1:
The patent combines multiple metrology targets for different patterning steps into a single integrated metrology target. This single target contains features from both the first and second patterning steps, allowing overlay measurements for multiple layers to be performed simultaneously in a single measurement operation, thereby halving the measurement time while maintaining measurement precision
Solution Approach 2:
The single metrology target is designed to serve multiple functions by incorporating features from different patterning steps. It can simultaneously provide overlay measurement capabilities for both the first and second patterning steps, making the metrology system more efficient and reducing the total number of separate measurements required
2Measurement precision
If separate metrology targets are used for each patterning step, then overlay measurement can be performed for each layer, but the substrate area occupied by metrology targets increases
Solution Approach 1:
The patent merges multiple separate metrology targets into a single integrated target structure. This consolidation reduces the total substrate area required for metrology from the sum of multiple separate target areas to a single compact target area, while still providing comprehensive overlay measurement capabilities for all patterning steps
Solution Approach 2:
The single metrology target utilizes vertical layering and three-dimensional structuring to accommodate features from multiple patterning steps. By stacking and arranging measurement features in different layers and spatial configurations within a single target, the design achieves multi-functionality without proportionally increasing the lateral footprint on the substrate
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient overlay measurement without increasing the substrate area or measurement time, allowing for accurate positioning of product features and reducing the overhead in metrology, thus improving process control in high-volume manufacturing.
Implementation Method 1
These devices direct a beam of radiation onto a target and measure one or more properties of the scattered radiation e.g., intensity at a single angle of reflection as a function of wavelength; intensity at one or more wavelengths as a function of reflected angle; or polarization as a function of reflected angle
Implementation Method 2
Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate
Implementation Method 3
A patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern
Data Source
AI summary
Disclosed is a method of measuring overlay between upper and lower layers on a substrate using metrology targets formed by a lithographic process. The lithographic process is of a multiple-patterning type whereby first and second distinct populations of structures are formed in a single one of said layers (L1) by respective first and second patterning steps. The metrology target (620) in the single one of said layers comprises a set of structures of which different subsets (642A, 642B) are formed in said first and second patterning steps. An overlay measurement on this target can be used to calculate a combined (average) overlay performance parameter for both of the first and second patterning steps.